Multiple cathode indicator tube having no obstruction in the form of support disks



Dec. 12, 1967 ROSENBERG, JR ET AL 3,358,176

MULTIPLE CATHODE INDICATOR TUBE HAVING N0 OBSTRUCTION 1 IN THE FORM OF SUPPORT DISKS 2 Sheets-Sheet 1 Filed July 19, 1965 J.'/\/. HUUmHNE E; -/Wa\ m HT U NE 3,358, 76 MULTIPLE CATHODE INDICATOR TUBE HAVING no DESTRUCTION Dec. 12, 967 F. o. ROSENBERG. JR. T

IN THE FORM OF SUPPORT DISKS 7 Filed July 19, 1965 2 Sheets-Sheet 2 United States Patent 3,358,176 MULTIPLE CATHODE INDICATOR TUBE HAVKNG N0 OBSTRUCTION IN THE FORM OF SUPPORT DISKS Fred 0. Rosenberg, Jr., Colouia, and John N. Hoomans, Martinsville, Ni, assiguors to Burroughs Corporation, Detroit, Mich, a corporation of Michigan Filed July 19, 1965, Ser. No. 472,887 13 Claims. (Cl. 313-1095) ABSTRACT OF THE DISCLOSURE The disclosure is of a multiple cathode indicator tube which comprises a gas-filled envelope containing a stack of electrodes facing the viewing window of the envelope with no obstruction in the form of support disks of the like present between the stem and the dome of the envelope. The stack of electrodes includes a curved rear anode plate and a curved front anode screen and a group of cathode electrodes between them. The anode plate and screen form a generally tubular anode which completely encloses the front, rear, and sides of the group of cathode electrodes.

For support of the electrode assembly, the rear anode plate is welded to one or more tube pins and two support posts extend from the rear anode plate to support the cathode electrodes. A metal disk operable as a decimal point is positioned at the side and adjacent to the lower ends of the cathodes and is supported either by the back anode plate or by a tube pin.

This invention relates to cold cathode gaseous glow tubes and, particularly, to cathode glow indicator tubes for displaying characters such as numbers, letters, or the like.

One type of indicator tube which has been available commercially for many years is known as a Nixie tube and is made and sold by Burroughs Corporation. The most popular commercial form of this tube includes a stack of cathode electrodes mounted parallel to each other in a metallic cup-shaped anode electrode and facing a viewing window at the end of the tube envelope. This type of tube is thus known as an end-view tube. The cathode electrodes are oriented parallel to the base of the tube in which the tube pins are mounted, and the cathodes are shielded from the tube pins by the anode cup and by an assembly of insulating disks. This tube thus includes a relatively large number of components, which are provided primarily for the purpose of insulating and supporting the electrode structure and for shielding the cathode leads and tube pins from other components to prevent these leads and pins from glowing. These components represent a cost factor in both material and assembly time which it would be desirable to eliminate, if possible. In mass production operation, such savings can be important. Similar indicator tubes which have appeared on the market are also subject to the same criticism.

Cathode glow indicator tubes are also constructed as side-view tubes, with a stack of electrodes mounted in the tube envelope perpendicular to the tube base and facing the side of the tube envelope. Tubes of this construction present somewhat greater problems than the end-view tube in providing a rugged mounting arrangement for the electrodes Within the tube. Thus, these tubes also require a relatively large number of auxiliary elements to provide a satisfactory structure.

The objects of the present invention concern the provision of an improved multiple cathode indicator tube which is of a simple but rugged construction.

The objects of the invention also relate to the provi- 3,358,176 Patented Dec. 12, 1967 sion of a multiple cathode indicator tube having an electrode construction which utilizes a minimum number of component parts.

The objects of the invention also relate to the provision of an improved multiple cathode side-view indicator tube.

Briefly, an indicator tube embodying the invention includes a gas-filled envelope which is generally elongated and has at one end a dome, at the other end a pin-carrying stem, and in between, a viewing window. An electrode assembly mounted inside the envelope includes an anode plate mounted remote from the viewing window and generally parallel to the tube pins and to the longitudinal axis of the envelope. The anode plate carries two support posts on which there is mounted a stack of cathode electrodes facing the viewing window and electrical-1y connected to the tube pins by means of cathode leads. The entire electrode assembly is rigidly and directly secured to the tube pins in simple fashion, with no structural elements such as auxiliary support plates or the like being required. In the construction of this tube, the tube pins and cathode leads are selected or processed, generally by heating, to have a higher work function than the cathodes themselves. This results in a tube having a free and unobstructed path from the stem through the cathode stack to the dome of the envelope. With such a construction, cathode sputtering is minimized, and lead and pin glow is avoided, even when the tube is operated at relatively high currents, higher than that which has been considered normal in prior tubes.

The invention is described in greater detail with reference to the drawings wherein:

FIG. 1 is an isometric view of an indicator tube embodying the invention;

FIG. 2 is a side "iew of the tube of FIG. 1;

FIG. 3 is a View of a typical cathode and cathode lead arrangement;

FIG. 4 is a view of one form of decimal point construction for the tube of the invention;

FIG. 5 is a view of another form of decimal point construction;

FIG. 6 is a side view of a modification of a portion of the invention; and

FIG. 7 is a front view of a modification of another portion of the invention.

An indicator tube 18 embodying the invention includes an envelope 26 which contains a gas suitable for supporting cathode glow. Such a gas may be argon, neon, or the like, at a pressure which may be in the range of about 30 to about mm. of mercury. If desired, other substances such as mercury may be added in small quantities to the gas content of the envelope.

The envelope 2% is generally elongated and its side Wall 22 comprises a viewing window so that the tube is what may be called a side-view indicator tube. The envelope includes a base or stem 24 through which metal pins 28 or other conductive leads extend, and by means of which electrical connection is made from the electrodes within the tube to external electrical circuitry. All of the pins 28, except at least two adjacent pins 28', extend to substantially the same height within the envelope and terminate in a common plane which is transverse to the longitudinal axis of the envelope. The tube pins are pref.- erably disposed on a circular locus. The two pins 28 are somewhat longer than the others inside the envelope for a purpose to be described. The upper end 30 of the envelope, remote from the stem, is known as the dome of the envelope and carries a tubulation 32 for evacuating the envelope and filling it with the necessary gaseous atmosphere. If desired, the tubulation might be provided in the stem 24.

The electrode assembly mounted inside the envelope 20 includes a cup-shaped or trough-shaped back plate 36 which serves as an anode electrode and includes a pair of apertures, in which an upper suport post 49 and a lower support post 44 are insulatingly mounted. The posts or rods 40 and 44 are either made of an insulating material such as a ceramic, or of metal coated with glass, or the like. For support of the posts on the anode plate, washers 50 are mounted on the posts on either side of the back plate 36, and a metal eyelet 56 is mounted on the back end of each post and crimped in place to hold the washers 50 and the posts in place.

The anode plate 36 is, in general, a large-area plate which extends along a considerable portion of the length of the envelope, with a central panel 66 and two opposed side panels 64, 68 oriented at an angle thereto so that they bend toward the viewing window. If desired, the side panels 64 and 68 need not be oriented at an angle to the central panel, but may lie in the same plane, in which case, the anode 36 would be a large-area flat plate. T12; support posts 40 and 44 extend parallel to each other, and are located near the opposite ends of the anode plate 36 in vertical alignment with each other on a line which extends vertically along the center of the back plate. The anode plate is rigidly secured by welding, for example, to the two elongated tube pins 28' to provide a strong and rigid connection which is the primary support for the electrode assembly to be described further below. The lower support post 44 is thus positioned closely adjacent to the inner ends of the tube pins 23. The pins 28 may be of one-piece construction, or they might comprise extensions welded to pins 28.

The electrode assembly also includes a plurality of cathode electrodes 76 in the form of characters, usually including numerals to 9. To simplify the drawing, the cathode electrodes are omitted in FIG. 1 and are shown in FIG. 2. The cathode electrodes are of metal such as stainless steel, nickel, molybdenum, or the like, and are relatively filamentary in construction. The cathode electrodes are generally elongated and may be considered to have a long axis, and they are provided with apertured mounting tabs 80 at opposite ends which may be considered to be the ends of the axis of each cathode. The tabs may be generally U-shaped or annular (FIG. 3), and the cathodes are mounted and secured on the support posts 40 and 44 by means of the apertured tabs which engage or are threaded on the support posts 40 and 44. The cathodes are insulated from each other by means of washers 50 which are threaded on the support posts between the cathodes. If desired, one or more auxiliary electrodes 76', which may be duplicate cathode numerals, may be mounted at different locations along the stack of cathode electrodes for operation as anodes or simply for support.

A cathode lead 90 is provided for making electrical connection between each cathode electrode and one of the tube pins 28. This lead may be an integral extension from the lower mounting tab of each cathode, or it may be a separate lead having its own apertured tab 91 as shown in FIG. 3, by means of which it is threaded on the lower support post between each cathode and an insulating spacer 50. Each cathode thus has a lead which extends from its lower tab 80 to one of the tube pins 28 to which it is welded.

In the completed tube, it is preferable that the cathodes 76 have a lower work function than the cathode leads 90 and tube pins 28 so that, when operating potentials are applied between the anode and a cathode, the cathode exhibits cathode glow, but the associated cathode lead 90 and tube pins 28 do not glow. To achieve this result, the cathodes 76 may be of a different material than the leads 90 and pins 28, or, alternatively, the cathodes and leads may be of the same material but the leads are provided with a coating such as an oxide to increase their work function. The tube pins 28 also may be oxidized, although they, in any case, are generally of a different material than the cathodes and the cathode leads. A chrome-iron alloy is commonly used for the pins 28.

A relatively fine mesh screen electrode 100, which is normally used as part of the anode assembly of the tube, is mounted on the posts 40 and 44 at the top of the stack of cathodes 76, with an insulating spacer 50 between it and the adjacent cathode, and all of the electrodes, including the screen, are locked in place on the support posts by means of a metal eyelet 106 or the like mounted at the front end of each support post and secured in place by crimping or the like. The mesh screen is generally trough-shaped and includes a relatively largearea front panel 110 which is located between the cathode electrodes and the viewing window of the envelope and has an area substantially equal to, or somewhat larger than, the area defined by the cathode electrodes. The screen also includes side panels 114, 116 which extend rearwardly and engage the back anode plate. The screen and the anode plate are either secured together, or they may merely touch without a permanent connection being made, as desired. The screen 100 may also be electrically connected to a pin 28 by a suitable lead or tab.

The tube 10 also includes cathode electrode means for representing a decimal point. In one arrangement (FIG. 1), this is formed by a post 130, similar to posts 40 and 44, and insulatingly secured to the central panel of the anode plate at the lower portion thereof and on the left, or if desired, the right, side of the stack of cathodes as viewed end on. The post is located at a position with respect to the cathode numerals in the tube which a decimal point would normally occupy. The post 130 extends from the anode plate toward the viewing window and parallel to the support posts 40 and 44, and it is electrically connected by a lead 134 to a pin 28. Preferably, post 130 is itself insulated, but it carries at its outer end a metal disk having a low Work function and adapted to provide cathode glow when an appropriate voltage is applied to lead 128. Disk 140 has an area sufiicient to provide the desired area of glow for the decimal point. The decimal point post 130 may be relatively short and need not be as long as the support posts 40, 4-4 to perform the desired function.

In another arrangement shown in FIG. 4, the decimal point is formed by directly attaching a metal disk to a suitably elongated tube pin 28" which is properly positioned in the stem and is at the desired height for a decimal point. In still another arrangement shown in FIG. 5, an auxiliary tab 154 which carries disk 150 is secured to post 28" and is arranged to support the decimal point at the desired location in the tube. In all cases, disk 150 has a work function which is lower than that of the posts or tabs which support it so that it glows and its support members do not glow.

It is clear that the decimal point disk may be located at any desired position in the tube 10 for providing representations other than the strict decimal point representation.

For optimum operation and long life, the tube 10 includes in its atmosphere a small proportion of mercury vapor which serves to minimize cathode sputtering during tube operation. The mercury may be provided in any suitable fashion. For example, it may be introduced directly with the other gases, such as neon and argon, or, in a preferred arrangement, it is provided in a glass capsule which is surrounded by a coil of heating wire connected between two pins 28. Heating of the wire by current flow causes the mercury to expand and fracture the capsule, whereby the mercury vapor escapes into the tube atmosphere.

A modified arrangement for interconnecting the anode plate 36, the front screen 100, and the support posts 40 and 44 is shown in FIG. 6. In this arrangement, the apertures in the anode plate and the screen and 192, respectively, which are to receive the support posts are provided with permanently mounted eyelets 198 and 200,

respectively, in which the posts 40 and 44 are inserted. The eyelets are crimped to secure the support posts in place. As above, a glass sleeve or coating 210 is provided on the support posts 40 and 44 between the anode and screen and between eyelets 198 and 200 to insulate the cathodes 76 from the support posts. The cathodes and their leads (not shown in FIG. 6) are mounted on the support posts in the manner described above, with all metal parts being suitably insulated and particularly with the cathodes being insulated from the anode plate 36 and front screen 100 by means of one or more insulating spacers 50. It is to be noted that the eyelets are only long enough to provide secure engagement with the support posts, and that the glass sleeve is of sufficient length so that all cathodes are insulated from the support posts thereby.

It can be seen that a continuous electrical connection exists from screenltlt), eyelet 200, post 40 (and 44), eyelet 19S, anode plate 36, and pins 28 or 28'.

In another arrangement, shown in FIG. 7, for securing the anode plate to the tube stem, the lower edge 220 of the anode plate itself is provided with two or more depending tabs 230 which are welded to tube pins 28. With this arrangement, the tube pins 28 may all be of the same length.

In; the manufacture of the tube 10, generally, the stem is prepared first, and the tube pins 28, 28' are oxidized in any suitable fashion, for example, by heating in the presence of oxygen. The'cathode numerals are thoroughly cleaned, and, if the leads are integral therewith, the leads are oxidized. If the cathode leads are separate elements, they are cleaned and oxidized in similar fashion. The anode and cathode electrodes are then assembled, and the assembly is mounted on the stem with the pins 28 welded to the anode plate and the cathode leads welded to pins 28. Next, the tube is evacuated by means of a suitable tubulation either in the stem or in the dome of the envelope, and the envelope is filled with a suitable gas, for example, neon, argon, or the like at a pressure of about 85 mm.

After the tube has been assembled, it is aged in the following manner. First, all of the cathodes are caused to glow at the same time by the application of a suitable potential between all of the cathodes and the anode. In a tube having ten cathodes shaped as to 9 and with the cathodes being about one inch in length and with the strokes of the cathodes being about of an inch in width, total current of about 8 ma. flows for about one hour during this step. Next, for approximately a fourhour period, the cathodes are energized sequentially and caused to glow one at a time for a fraction of a second with a cathode cur-rent flow of about 6 ma. This step is known as dynamic cycling. Next, the mercury is released from the capsule and the final aging step is carried out. This step comprises cycling the cathodes at a current flow of about 3 ma. for about forty-eight hours.

The indicator tube of the invention has many advantages, and it is clear from the foregoing description that one of the important advantages is the simplicity and openness of its construction. Since the tube includes a minimum number of parts, a saving results both in the cost of parts and in the time and labor involved in assembling the tube. Another advantage which arises from the simple and open construction is the optimum viewability of any cathode number in the stack when viewed from side to side or from almost any angle. Also, in operation, it has been found that the tube of the invention can be operated satisfactorily without cathode lead or tube pin glow at relatively high currents of the order of about 7 to about 10 ma. Comparable tubes in the prior art could only be operated satisfactorily with a maximum current of about 3 ma., after which cathode lead or tube pin glow appeared. It has been noted that, in the tube of the invention, cathode sputtering and the deposit of sputtered cathode material on tube parts, particularly cathode spacers, is at a minimum. It is theorized that the simple, open construction provides ion or current flow paths from tube stem through the stack of electrodes to the dome of the envelope, and this minimizes the sputtering of cathode material.

What is claimed is:

1. A cathode glow indicator tube including an envelope which is elongated in the vertical direction and has a stem, a dome, and a viewing window extending along the length of the envelope,

the envelope being filled with a gas capable of supporting cathode glow and having tube pins sealed in said stem,

said tube pins extending into said envelope,

a curved rear anode plate and a curved front anode screen in electrical contact with each other and forming together a single, open-ended generally tubular anode,

a stack of cathode electrodes positioned within said tubular anode and facing said viewing window through said anode screen, said cathode electrodes having mounting tabs and being formed as characters to be viewed through said viewing window,

a pair of insulated upper and lower support posts secured between said rear anode plate and said front anode screen to form a rigid unitary anode assembly, said posts being spaced apart parallel to each other with said cathode electrodes mounted thereon by means of said mounting tabs,

said rear anode plate being secured to a plurality of said tube pins to provide the primary support for said anode and said stack of cathode electrodes, and

a connecting lead from each cathode to a tube pin,

the space in said envelope extending between said stem through said stack of electrodes'to the dome of said envelope being open and unobstructed whereby gas ions have a free and unobstructed flow path along the entire length of the envelope.

2. The tube defined in claim 1 wherein said tube pins inside said envelope have a different work function than said cathode electrodes whereby, when operating potentials are applied and current flows between said anode and a cathode, the cathode glows and the associated tube pin does not glow.

3. The tube defined in claim 1 and including insulating disks mounted on each support post between cathode electrodes to insulate them from each other, said disks being in contact with and having a larger area than said mounting tabs of said cathodes.

4. The tube defined in claim 1 wherein said support posts are in vertical alignment above and below each other, the lower post being positioned near said tube pins and the upper post being positioned near the upper end of said envelope, said posts including metallic portions which are electrically connected to said anode plate and said screen whereby said plate and screen together are operable as the tube anode.

5. The tube defined in claim 1 wherein said anode plate and said mesh screen carry pairs of aligned eyelets and said support posts are of metal and are secured between said plate and screen by being coupled between a pair of said eyelets, each support post carrying a body of insulating material between the pair of eyelets to which it is secured so that the cathode electrodes supported on the posts are insulated from the posts.

6. The tube defined in claim 1 and including a small metal disk coupled to a tube pin and positioned at the side and adjacent to the lower edges of said cathode electrodes, said disk being operable as a glow cathode to represent a decimal point.

7. The tube defined in claim 1 wherein said support posts are in vertical alignment above and below each other, the lower post being positioned near said tube pins and the upper posts being positioned near the upper end of said envelope, said connecting lead from each cathode electrode extending from the lower support post to a tube pin, said tube pins and connecting leads being oxidized to impart to them a higher work function than said cathode electrodes have.

8. A side-view cathode glow indicator tube comprising:

an elongated envelope containing a gaseous atmosphere capable of supporting cathode glow, said envelope including an elongated viewing window parallel to the principal axis of said envelope;

a base fixedly secured to one end of said envelope;

a plurality of lead-in pins extending through said base and into said gaseous atmosphere for individual connection to an electrical circuit;

a plurality of character-shaped cathode electrodes in a stacked, spaced-apart array, said cathode electrodes being arrayed in substantially parallel planes to face the viewing Window and each having an electrical connection with an individual lead-in pin, said cathode electrodes further including integrally formed tab means at opposite ends of said character electrodes for supporting said electrodes;

a plurality of spaced apart rods at least two of which engage said tab means at opposite ends of said cathode electrodes in an electrically insulating, supporting fashion;

an anode structure being structurally rigid and electrically continuous and including an anode plate positioned parallel to and behind the planes of said cathode electrodes relative to the viewing window and further including a screen member encircling the front and sides of said stacked electrode array;

said rods being supported adjacent to their ends by said anode plate and said screen member with their axes extending substantially parallel to one another and substantially normal to the viewing window and thereby supporting the cathode electrode stack within the anode structure;

said anode plate, said screen member and said rods in combination forming a rigid structure whereby the respective upper and lower ends of said anode plate and said screen member relative to the viewing window remain in substantially parallel spaced apart planes; and

means providing a rigid connection between the bottom portion of said anode plate and one or more '8 of the immediately adjacent lead-in pins for supporting the anode plate in fixed upright position in the tube and thus supporting the anode structure above the base end of the envelope.

9. The indicator tube as defined in claim 8 additionally including at least one disk-shaped cathode glow electrode supported within said encircling anode structure with its plane extending parallel to those of said character-shaped cathode electrodes, said at least one disk cathode electrode being positioned relative to said character-shaped cathode electrode array to function when selected to glow as a decimal point.

10. The indicator tube as defined in claim 9 wherein said at least one disk-shaped cathode glow electrode is carried by and electrically connected to one of said leadin pins.

11. The indicator tube as defined in claim 9 wherein said at least one disk-shaped cathode glow electrode is carried by one of said plurality of parallel extending rods and is electrically connected to one of said lead-in pins.

12. The indicator tube defined in claim 8 wherein said anode plate is constituted by a back member and a pail of flanges angularly turned toward the viewing window, wherein said screen member is supported in electrical contactual engagement with said anode plate proximate said flanges, and wherein cap means is employed for securing the ends of said rods to said back member and to said screen member respectively.

13. The indicator tube defined in claim 8 wherein said anode structure is open ended and provides a substantially unobstructed ion flow space extending through said stack of cathode electrodes from said base to the opposite end of said envelope.

References Cited UNITED STATES PATENTS 6/1965 Van den Berg 313-1095 5/1966 Frouws et a1. 313-1095 ROBERT L. JUDD, DAVID J. GALVIN,

Assistant Examiners. 

1. A CATHODE GLOW INDICATOR TUBE INCLUDING AN ENVELOPE WHICH IS ELONGATED IN THE VERTICAL DIRECTION AND HAS A STEAM, A DOME, AND A VIEWING WINDOW EXTENDING ALONG THE LENGTH OF THE ENVELOPE, THE ENVELOPE BEING FILLED WITH A GAS CAPABLE OF SUPPORTING CATHODE GLOW AND HAVING TUBE PINS SEALED IN SAID STEM, SAID TUBE PINS EXTENDING INTO SAID ENVELOPE, A CURVED REAR ANODE PLATE AND A CURVED FRONT ANODE SCREEN IN ELECTRICAL CONTACT WITH EACH OTHER AND FORMING TOGETHER A SINGLE, OPEN-ENDED GENERALLY TUBULAR ANODE, A STACK OF CATHODE ELECTRODES POSITIONED WITHIN SAID TUBULAR ANODE AND FACING SAID VIEWING WINDOW THROUGH SAID ANODE SCREEN, SAID CATHODE ELECTRODES HAVING MOUNTING TABS AND BEING FORMED AS CHARACTERS TO BE VIEWED THROUGH SAID VIEWING WINDOW, A PAIR OF INSULATED UPPER AND LOWER SUPPORT POSTS SECURED BETWEEN SAID REAR ANODE PLATE AND SAID FRONT ANODE SCREEN TO FORM A RIGID UNITARY ANODE ASSEMBLY, SAID POSTS BEING SPACED APART PARALLEL TO EACH OTHER WITH SAID CATHODE ELECTRODES MOUNTED THEREON BY MEANS OF SAID MOUNTING TABS, SAID REAR ANODE PLATE BEING SECURED TO A PLURALITY OF SAID TUBE PINS TO PROVIDE THE PRIMARY SUPPORT FOR SAID ANODE AND SAID STACK OF CATHODE ELECTRODES, AND A CONNECTING LEAD FROM EACH CATHODE TO A TUBE PIN, THE SPACE IN SAID ENVELOPE EXTENDING BETWEEN SAID STEM THROUGH SAID STACK OF ELECTRODES TO THE DOME OF SAID ENVELOPE BEING OPEN AND UNOBSTRUCTED WHEREBY GAS IONS HAVE A FREE AND UNOBSTRUCTED FLOW PATH ALONG THE ENTIRE LENGTH OF THE ENVELOPE. 